Variable capacity scroll compressor

ABSTRACT

Disclosed is a variable capacity scroll compressor including an intake passage connected to an intake chamber, an exhaust passage connected to an exhaust chamber, a bypass port formed through a wall defining a compression space, a bypass passage having a first end connected to the bypass port and a second end connected to the intake chamber that is in a low-pressure state, a check valve for selectively connecting the bypass passage to the bypass port, and a control valve for selectively applying one of low-pressure fluid and high-pressure fluid in the exhaust passage to the check valve to control the check valve to one of opening and closing positions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a scroll compressor, and moreparticularly, to a variable capacity scroll compressor, which isconfigured to vary a compression capacity according to a simpleoperation of a system where the compressor is applied.

2. Description of the Related Art

Generally, a cooling system is applied to an air conditioner or arefrigerator to lower the temperature of an enclosed space by absorbingand discharging heat using refrigerant circulating a cooling cycle.

Such a cooling system is configured to perform a series of cycles ofcompression, condensation, expansion and vaporization of refrigerant. Ascroll compressor is used to perform the compression cycle among theseries of cycles.

Since the scroll compressor is disclosed in a plurality of publisheddocuments, the detailed description on the general structure andoperation will be omitted herein.

The reason why the compression capacity of a scroll compressor should bevaried will be described hereinafter.

A scroll compressor for a specific use is generally selected byconsidering the most disadvantageous operation condition whenforecasting its use environment, for instance, the greatest compressioncapacity-requested condition (i.e., a heating operation of an airconditioner using heat pump).

However, it is general that the most disadvantageous condition does notnearly occur in an actual operation. In an actual operation of thecompressor, a condition needing a small compression capacity (ex.cooling operation of air conditioner) not the most disadvantageouscondition exists too.

Thus, when the compressor having a large compression capacity isselected considering the worst condition, the compressor is operatedunder the low-load condition during an operation period of thehigh-compression ratio, thereby deteriorating an overall operationefficiency of the system.

Therefore, in order to improve the overall operating efficiency evenunder a normal operating condition and to accept the operationalcondition under the most disadvantageous condition, there is a need fora compressor that has a variable compression capacity.

To vary the compression capacity of the scroll compressor, a method forelectrically controlling an RPM of the compressor has been most widelyused.

Such an electrical control method has an advantage of effectivelyvarying the compression capacity. However, additional components, forinstance, an inverter for accurately controlling the RPM of a motor, arerequired. Furthermore, when the motor rotates with a relatively highRPM, it is difficult to ensure a reliability of frictional portions.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a variable capacityscroll compressor that substantially obviates one or more problems dueto limitations and disadvantages of the related art.

An object of the present invention is to provide a variable capacityscroll compressor that can vary a compression capacity using a bypassfunction in a state where a compressor motor rotates at a constant RPM.

Another object of the present invention is to provide a variablecapacity scroll compressor that can vary a compression capacity byoperating a valve using either uncompressed low-pressure fluid orcompressed high-pressure fluid.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein,there is provided a variable capacity scroll compressor including: abypass port formed through a wall defining a compression space; a bypasspassage having a first end connected to the bypass port and a second endconnected to an intake chamber that is in a low-pressure state; a checkvalve for selectively connecting the bypass passage to the bypass port;and a control valve for selectively applying one of low-pressure fluidand high-pressure fluid in an exhaust passage to the check valve tocontrol the check valve to one of opening and closing positions.

In another aspect of the present invention, there is provided a variablecapacity scroll compressor including: a bypass port formed on acompression path defined between first and second scroll members; acheck valve for controlling opening and closing states of the bypassport; and a bypass controller for controlling an opening/closingoperation of the check valve using at least pressure applied from anexhaust passage.

In still another aspect of the present invention, there is provided avariable capacity scroll compressor including: a bypass port formed on acompression path defined between first and second scroll members; afloat valve for controlling opening and closing states of the bypassport; and a bypass controller for controlling an operation of the checkvalve by high-pressure fluid applied from an exhaust passage.

According to the present invention, the capacity variation of the scrollcompressor can be easily varied without adding additional components.

The present invention has an advantage the inventive compressor can beeffectively used when it is employed to a system where a capacityvariation is required.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a sectional view of a scroll compressor according to a firstembodiment of the present invention;

FIG. 2 is a bottom view of a stationary scroll member depicted in FIG.1;

FIG. 3 is an enlarged view of a portion “A”of FIG. 1, in which a bypassport is closed;

FIG. 4 is a view conceptually illustrating a state of a scroll memberwhen a bypass port is closed;

FIG. 5 is an enlarged view of a portion “A” of FIG. 1, in which a bypassport is opened;

FIG. 6 is a view conceptually illustrating a state of scroll member whena bypass port is opened; and

FIG. 7 is a sectional view of a scroll compressor according to a secondembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

FIG. 1 shows a sectional view of a scroll compressor according to anembodiment of the present invention.

Referring to FIG. 1, the inventive scroll compressor includes aconventional compressing part, a bypass part for varying a compressioncapacity, and a bypass control part for controlling the bypass part.

The conventional compressing part includes a seal case 11 for definingan enclosed chamber, a seal plate 12 disposed in the seal case 11 todivide the sealed chamber into a low-pressure intake chamber 13 and ahigh-pressure exhaust chamber 14, an intake passage 22 connected to theintake chamber 13 to supply fluid to be compressed to the intake chamber13, an exhaust passage 23 connected to the exhaust chamber 14 to exhaustcompressed fluid out of the exhaust chamber 14, a stationary scrollmember 15 fixed on an inner circumference of the seal case 11, a drivingshaft 19 extending from a motor (not shown) and having an eccentricupper end, a orbiting scroll member 16 associated with the driving shaft19, a stationary spiral wrap 17 formed on the stationary scroll member15, a rotational spiral wrap 18 defining the fluid compressing path bysurface-contacting the stationary spiral wrap 17, a bearing 21 forstably supporting the driving shaft 19, and a central exhaust passage 26formed through a central axis of the stationary scroll member 15 todirect the compressed fluid to the exhaust chamber 14.

The bypass part includes a bypass port 24 formed through a portion ofthe stationary scroll member 15, a check valve 25 formed on a rear sideof the bypass port 24 to control the flowing direction of the fluid, anda bypass passage 31 branched off from the check valve 25 to allow thefluid exhausted through the bypass port 24 to be directed to the intakechamber 13.

The bypass control part includes a control passage 30 for formingcontrol pressure for controlling an opening/closing operation of thecheck valve 25 and a control valve 29 for allowing the control pressureformed on the control passage 30 to be selectively supplied from one ofthe low-pressure and high-pressure passages 27 and 28. The controlpassage 30 is formed penetrating the seal plate 12 to communicate with acompression space of the conventional compressing part.

Particularly, the low-pressure passage 27 has a first end connected tothe control valve 29 and a second end connected to the intake passage 22so that low-pressure of the intake passage 22 can be applied to thelow-pressure passage 27. The high-pressure passage 28 has a first endconnected to the control valve 29 and a second end connected to theexhaust passage 23 so that high-pressure of the exhaust passage 23 canbe applied to the high-pressure passage 28.

Meanwhile, the check valve 25 may be formed of a float valve having afloating member moving in a direction where pressure is applied tochange a passage connection state.

For example, as shown in the drawing, a cylindrical member is disposedin a cylindrical housing, being movable in a direction wherelow-pressure is applied.

Alternatively, a check ball may be movably disposed in a housing so thata fluid passage hole can be opened or closed by the check ball. That is,any types of valves that are designed to be controlled by pressure canbe employed to the present invention.

In addition, the control valve 29 can be formed of a solenoid valvecontrolled by a predetermined controller.

The operation of the above described variable capacity scroll compressorwill be described hereinafter.

When the driving shaft 19 is rotated by the motor (not shown), theorbiting scroll member 16 associated with the driving shaft 19 rotates.At this point, the stationary scroll member 15 is in a fixed state.

When the orbiting scroll member 16 rotates, low-pressure fluid stored inthe intake chamber 13 is directed into a space defined between therotational spiral wrap 18 formed on the orbiting scroll member 16 andthe stationary spiral wrap 17 formed on the stationary scroll member 15,and is then compressed in the space.

The compressed fluid is directed into the exhaust chamber 14 through thecentral exhaust passage 26 formed through the central axis of thestationary scroll member 15, and the high-pressure fluid in the exhaustchamber 14 is exhausted through the exhaust passage 23.

Meanwhile, when the check valve 25 is closed (when the check valve 25 ismoved downward in the drawing), the fluid cannot be exhausted throughthe bypass port 24. However, when the check valve 25 is opened (when thecheck valve 25 is moved upward in the drawing), the fluid is exhaustedthrough the bypass port 24, and is then bypassed into the intake chamber13 through the bypass passage 31. Therefore, when the check valve 25 isopened, the compression capacity is reduced.

To control the operation of the check valve 25, the bypass control partfurther includes a control passage, one end of which is connected to thecheck valve 25 to applied control pressure to the check valve 25. Thecontrol valve 29 is formed on the other end of the control passage 30.By the control valve 29, one of the fluid pressures from thelow-pressure and high-pressure passages 27 and 28 is selected andapplied to the control passage 30.

Particularly, the low-pressure and high-pressure passages 27 and 28 arerespectively connected to the intake and exhaust passages 22 and 23 suchthat low-pressure fluid that is not compressed in the conventionalcompressing part and high-pressure fluid that is compressed in theconventional compressing part can be respectively supplied to thelow-pressure and high-pressure passages 27 and 28. As a result, thecontrol passage 30 is selectively supplied with one of the low-pressureand high-pressure fluids in the respective low-pressure andhigh-pressure passages 27 and 28.

Describing more in detail, when the high-pressure passage 28 isconnected to the control passage 30 by the control valve moved upward inFIG. 1, since the control passage 30 is supplied with the high-pressure,the check valve 25 is closed by moving downward. When the check valve 25is closed, since the bypass port 24 is closed, the fluid beingcompressed cannot be bypassed. As a result, a relatively large amount offluid can be compressed without any compression capacity loss.

When the low-pressure passage 27 is connected to the control passage 30by the control valve moved downward FIG. 1, since the low-pressure isapplied to the control passage 30, the check valve 25 is opened bymoving upward in FIG. 1. That is, pressure of fluid being compressed bya mutual operation of the scroll members 15 and 16 is lower than that inthe intake pressure 22, the check valve 25 that is the floating valve isopened.

In addition, when the check valve 25 is opened, since the bypass port 24is opened, the fluid being compressed is bypassed into the intakechamber 13 through the bypass passage 31. Therefore, the compressioncapacity is reduced as much as an amount of fluid bypassed.

FIG. 2 shows a bottom view of the stationary scroll member 15 depictedin FIG. 1.

Referring to FIG. 2, the stationary spiral wrap 17 is formed on thestationary scroll member 15, and the central exhaust passage 26 isformed through the central portion of the stationary spiral wrap 17. Thebypass port 24 is formed on the scroll member in a compression spacedefined by the stationary spiral wrap 17, thereby allowing the fluidbeing compressed to be bypassed.

FIGS. 3 and 5 show enlarged views of a portion “A” in FIG. 1, and FIGS.4 and 6 show views conceptually illustrating a scroll member accordingto opening and closing states of a bypass port. FIGS. 3 and 4 show astate where the bypass port is closed, and FIGS. 5 and 6 show a statewhere the bypass port is opened.

Referring first to FIG. 3, the bypass port 24 is formed at a positionbetween spaced parts of the spiral wrap 17, and is in a closed state bythe check valve 25. At this time, since high-pressure is applied to thecheck valve 25 through the control passage 30, the check valve 25 firmlycloses the bypass port 24.

Referring to FIG. 4, when the bypass port 24 is closed, a first intakevolume 41 that is a compression space defined between the stationaryspiral wrap 17 and the orbiting spiral wrap 18 can be formed from astart position where the stationary spiral wrap 17 meets the orbitingspiral wrap 18.

The intake volume will be described more in detail hereinafter.

The intake volume defined between the stationary and orbiting spiralwraps 17 and 18 contacting each other may include two intake volumes.

One is a first intake space defined when an inner circumference of thestationary spiral wrap 17 meets an outer circumference of the orbitingspiral wrap 18. The first intake space can be illustrated as the firstintake volume 41 depicted in FIG. 4.

The other is a second intake space (not shown) when an outercircumference of the stationary spiral wrap 17 meets an innercircumference of the orbiting spiral wrap 18. Although the second intakespace is not shown in the drawing, it can be assumed that the secondintake space can be formed by the orbiting operation of the orbitingspiral wrap 18.

A start point of the first intake space is defined on a locationindicated by the reference character SC1 (Compress Start 1), and a startpoint of the second intake space is defined on a location indicated bythe reference character SC2 (Compress Start 2. Since the start pointsSC1 and SC2 are not symmetrically located, this can be called anasymmetry operation mode. That is, when the scroll member is dividedinto half-and half based on the central portion of the scroll member andboth the start points SC1 and SC2 are sided to one half, this can becalled the asymmetric operation mode.

Referring to FIG. 5, when the bypass port 24 is opened by the checkvalve 25 moved upward, since the control passage 30 is supplied with thelow-pressure as described above, the check valve 25 is opened to allowthe fluid being compressed to be bypassed into the intake chamber 13through the bypass port 24 and the pass passage 31.

Referring to FIG. 6, in a state where the bypass port 24 is opened, astart point of a second intake volume 42 defined between the stationaryspiral wrap 42 and the rotational spiral wrap 18 is not defined on alocation where the stationary spiral wrap 17 firstly meets therotational spiral wrap 18. That is, it can be noted that a start pointof the second intake volume 42 is defined on a location passed over thelocation where the bypass port 24 is formed.

The intake volume formed when the bypass port is opened will bedescribed more in detail.

In this case, the intake volume defined between the stationary androtational spiral wraps 17 and 18 contacting each other may be alsodivided into first and second volumes.

The first volume is a first intake space defined when an innercircumference of the stationary spiral wrap 17 meets an outercircumference of the rotational spiral wrap 18. The first intake spacecan be illustrated as the second intake volume 42 depicted in FIG. 6.

The second volume is a second intake space (not shown) when an outercircumference of the stationary spiral wrap 17 meets an innercircumference of the rotational spiral wrap 18. Although the secondintake space is not shown in the drawing, it can be assumed that thesecond intake space can be formed by the rotational operation of therotational spiral wrap 18.

In addition, since the bypass port 24 is formed near the innercircumference of the stationary spiral wrap, it does not interfere withthe formation of the second intake space. However, the second intakespace is formed only when the bypass port 24 is closed by a thickness ofthe rotational spiral wrap 18. That is, although the second intake spaceis not affected by the presence of the bypass port 24 by the rotationalspiral wrap 18, an amount of fluid that is bypassed can be furthervaried in accordance with a thickness of the rotational spiral wrap 18and a relative location of the bypass port 24 formed in the compressionspace. When the bypass port 24 is formed on a sidewall defining thecompression space, the second intake space can be formed regardless ofthe thickness of the rotational spiral wrap.

In the beginning of the compression, a start point of the first intakespace is defined on a location indicated by the reference character CS1,and a start point of the second intake space is formed on a locationindicated by the reference character CS2. That is, the start points CS1and CS2 are symmetrically located based on the centers of the scrollmembers 15 and 16. This can be called a symmetry operation mode.

Meanwhile, in order to realize the perfect symmetry operation mode, thebypass port 24 is formed on an opposite side of a spiral start point ofthe stationary spiral wrap 17 based on the center of the stationaryscroll member 15.

When comparing the first intake volume 41 depicted in FIG. 4 with thesecond intake volume 42 depicted in FIG. 6, it can be noted that theyare different from each other.

The first intake volume 41 is greater than the second intake volume 42.This shows that, in the asymmetry operation mode, much more fluid can becompressed. However, the second intake space formed in the asymmetryoperation mode may be identical to that formed in the symmetry operationmode.

That is, since the volume of the intake space is varied according to astate (an open/close state) of the bypass port 24, the compressioncapacities defined by the first intake volume 41, formed when the bypassport is closed, and by the second intake volume 42, formed when thebypass port is opened, are difference from each other.

According to a series of tests, it was noted that, when the bypass portis formed on the location proposed in the drawing, the compressioncapacity obtained by performing the compression using a possible maximumvolume tolerance (whole load) in a state where the bypass port 24 isclosed is increased by 18% as compared with that obtained by performingthe compression using a part of the compressible capacity (a partialload) in a state where the bypass port 24 is opened.

That is, the operation of the scroll compressor is changed into one ofthe symmetry and asymmetry operation modes according to a variety offactors such as the opening/closing state of the bypass port 24, theopening/closing state of the check valve 25, and the control state ofthe control valve 29. In addition, the intake volume of the scrollcompressor is increased or decreased in accordance with theopening/closing state of the bypass port 24, thereby varying thecompression capacity of the scroll compressor.

For example, when the control valve 29 is controlled such that thehigh-pressure passage 28 is connected to the control passage 30, thecheck valve 25 moves downward in the drawing, and the bypass port 24 isclosed. The start points of the first and second intake spaces areasymmetrically located to operate the scroll compressor in the asymmetryoperation mode, thereby increasing the compression capacity. Therefore,this asymmetry operation mode is suitable for, for example, a heatingmode of an air conditioner where a relatively large amount ofcompression capacity is required.

When the control valve 29 is controlled such that the low-pressurepassage 27 is connected to the control passage 30, the check valve 25moves upward in the drawing, and the bypass port 24 is opened. The startpoints of the first and second intake spaces are symmetrically locatedto operate the scroll compressor in the symmetry operation mode, therebyreducing the compression capacity. Therefore, this symmetry operationmode is suitable for, for example, a cooling mode of the air conditionerwhere a relatively amount of compression capacity is required.

The application of the compressor of the present invention is notlimited to the air conditioner that is used only for a descriptionexample. That is, the inventive compressor can be applied to any systemsrequiring a variable compression capacity.

FIG. 7 shows a scroll compressor according to a second embodiment of thepresent invention.

As shown in the drawing, the scroll compressor of this embodiment isidentical to that of the first embodiment except for a connectionstructure around the control valve.

In detail, a control passage 52, a control valve 53, and a high-pressurepassage 51 are same as those in the first embodiment. However, thelow-pressure passage 27 that is selectively connected to the controlpassage by the control valve in the first embodiment is not formed inthis embodiment.

When the low-pressure passage 27 is not formed, the low-pressure of theintake passage 22 is not applied to the control passage 52 even when thecontrol valve 53 moves downward in the drawing.

At this point, since internal pressure of the control passage 52 islower than medium-pressure of fluid being compressed in the conventionalcompressing part, the check valve 25 can be opened. That is, when thehigh-pressure that has been supplied via the high-pressure passage 51and the control valve 53 is not supplied, the high-pressure fluid in thecontrol passage 52 is exhausted through the check valve 25 to realize apressure balance based on the check valve 25. Therefore, when thepressure balance is realized in the control passage 52 and thecompression space is formed in a high-pressure environment by theoperation of the scroll compressor, the check valve 25 that is in thepressure balance state is opened by the fluid being compressed.

As described above, by simply controlling the control valve, it ispossible to conveniently allow the fluid being compressed to bebypassed. Particularly, the mainspring of the control of the bypass portis to selectively use low-pressure formed by fluid that is not suckedinto the conventional compressing part and high-pressure formed by fluidcompressed by the conventional compressing part.

Therefore, the structure of the scroll compressor can be moresimplified, reducing the manufacturing costs.

The variable capacity scroll compressor according to the presentinvention has an advantage in that it is possible to vary thecompression capacity in multi-stages using a bypass function, which canbe realized by a simple structure, without varying the RPM of thecompression motor.

In addition, since the valve for realizing the capacity variation of thescroll compressor is designed to be controlled by fluid pressure that isnot still compressed in the compressing part and fluid pressure that iscompressed in the compressing part without adding additional components,the manufacturing cost of the scroll compressor can be saved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present invention. Thus,it is intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A variable capacity scroll compressor comprising: a bypass portformed through a wall defining a compression space; a bypass passagehaving a first end connected to the bypass port and a second endconnected to an intake chamber that is in a low-pressure state; a checkvalve for selectively connecting the bypass passage to the bypass port;and a control valve for selectively applying one of low-pressure fluidand high-pressure fluid in an exhaust passage to the check valve tocontrol the check valve to one of opening and closing positions.
 2. Thevariable capacity scroll compressor according to claim 1, wherein thecontrol valve is connected to (a) a low-pressure passage connected to anintake passage, (b) a high-pressure passage connected to the exhaustpassage, and (c) a control passage connected to the check valve, therebycontrolling an application of pressure.
 3. The variable capacity scrollcompressor according to claim 1, wherein the check valve is a floatvalve.
 4. The variable capacity scroll compressor according to claim 1,wherein the bypass port is formed at a stationary scroll member.
 5. Thevariable capacity scroll compressor according to claim 1, wherein thebypass port is formed at an orbiting scroll member.
 6. The variablecapacity scroll compressor according to claim 1, wherein the controlvalve is a solenoid valve.
 7. The variable capacity scroll compressoraccording to claim 1, wherein the bypass port is formed on an oppositeside of a location, where a start point of the compression space isformed, based on a center of a scroll member.
 8. The variable capacityscroll compressor according to claim 1, wherein the bypass port isformed at a location where the bypass port can be closed by a rotationalscroll wrap.
 9. The variable capacity scroll compressor according toclaim 1, wherein the low-pressure fluid is supplied through an intakepassage of the compressor.
 10. The variable capacity scroll compressoraccording to claim 1, wherein the control valve is connected to (a) ahigh-pressure passage connected to the exhaust passage and (b) a controlpassage connected to the check valve, thereby controlling an applicationof pressure applying.
 11. The variable capacity scroll compressoraccording to claim 1, wherein the control passage is formed penetratinga seal plate dividing a low-pressure side from a high-pressure side. 12.A variable capacity scroll compressor comprising: a bypass port formedon a compression path defined between first and second scroll members; acheck valve for controlling opening and closing states of the bypassport; and a bypass controller for controlling an opening/closingoperation of the check valve using at least pressure applied from anexhaust passage.
 13. The variable capacity scroll compressor accordingto claim 1, wherein the bypass controller comprises: a control valve forselectively supplying one of fluid pressure of an intake passage andfluid pressure of the exhaust pressure; and a control passage havingopposite ends respectively connected to the control valve and the checkvalve to apply the fluid pressure supplied from the control valve to thecheck valve.
 14. The variable capacity scroll compressor according toclaim 12, wherein the bypass controller comprises: a control valve forselectively supplying fluid pressure of the exhaust passage; and acontrol passage having opposite ends respectively connected to thecontrol valve and the check valve to apply the fluid pressure suppliedfrom the control valve to the check valve.
 15. The variable capacityscroll compressor according to claim 12, wherein fluid being compressedis exhausted to an intake chamber through the bypass port.
 16. Thevariable capacity scroll compressor according to claim 12, wherein thebypass port is designed to bypass fluid compressed in at least one oftwo intake spaces.
 17. The variable capacity scroll compressor accordingto claim 12, wherein the bypass port is defined between an innercircumference of a rotational scroll wrap formed on the first scrollmember and an outer circumference of a rotational scroll wrap formed onthe second scroll member.
 18. The variable capacity scroll compressoraccording to claim 12, wherein the check valve comprises a check ballthat is designed to freely move in a cavity by fluid pressure.
 19. Avariable capacity scroll compressor comprising: a bypass port formed ona compression path defined between first and second scroll members; afloat valve for controlling opening and closing states of the bypassport; and a bypass controller for controlling an operation of the checkvalve by high-pressure fluid applied from an exhaust passage.
 20. Avariable capacity scroll compressor according to claim 19, wherein, inorder to control the operation of the check valve, low-pressure fluidmay be further applied to the bypass controller from an intake passage.21. A variable capacity scroll compressor according to claim 19, whereinthe bypass port is formed at a location allowing for both of symmetryand asymmetry operation modes of the scroll compressor.
 22. A variablecapacity scroll compressor according to claim 19, wherein the bypassport is formed on a sidewall defining a compression space.